A non-peptide NIR fluorescent probe for detection of chymotrypsin and its imaging application

In this work, a turn-on near-infrared fluorescent probe, hemicyanine derivative (CyB), for the highly selective and sensitive detection of chymotrypsin was developed. The probe is fabricated by incorporating a recognition group of 4-bromobutyryl into the hemicyanine skeleton. Upon the nucleophilic substitution reaction of chymotrypsin and the probe, the probe displayed a remarkable fluorescence enhancement and a visible color change under natural light. This property can be utilized for the detection of chymotrypsin with a detection limit (LOD) of 0.013 U mL−1. Moreover, the cell and in vivo imaging experiments validated that this probe has the potential ability to detect chymotrypsin in biological systems and can provide a promising application prospect for screening chymotrypsin inhibitors.